I have a 1995 Blazer with 293,000 miles. Yep, rebuild at 217,500 after a cracked head gasket. Love this damn rig. Lots of good memories. Anyways, the other day while going uphill she started making a loud vacuum noise coming from the front passenger side. Has a new air filter and I checked all the hoses for leaks. Nothing. Am I possibly hearing the cat converter? If I knew where to look I'm sure I could fix it.
Thanks

 

I just took my 96 Blazer into the dealer for them to take a quick look.

Symptoms: I have a rattle at different RPMs, a major sucking sound anytime I get on the engine enough to downshift (hills, 2/3+ throttle, ect) and a big time loss of power, but only when I get on it.

I do have a missing TB to intake hold down bolt, but they said the noise AND a rattle coming from the lower passenger side was the CAT going bad and that the honeycomb is shifting, blocking air passage and that probably the leading cone gasket is whipped, causing the rattle and location of air escaping. This is odd since the noise started when I noticed a few hose clamps on the intake were loose and tightened them, so I figured it was sucking from the TB, but it's WAY loud and coming from below. I have the TB to intake hold down bolt on order, so well see.

 

just spent $380 on new cat and muffler. solved my power issue and the sucking noise turned out to be the exhaust not getting through the muffler because the contents of my cat were in the muffler.

 

CAT "Litter" in the Muffler. Nice!!! That sounds like my issue. Better then a blown head or ?? Thanks for the update.